The present invention relates to a method and apparatus for damping acoustic vibration and shielding electronic components of a disc drive from stray magnetic flux.
Disc drives of the xe2x80x9cWinchesterxe2x80x9d type are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are rotatably mounted to a base of the disc drive and are rotated via a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under a respective head. Each head includes a hydrodynamic (e.g. air) bearing slider in a transducer for writing information to and reading information from the disc surface. An actuator mechanism moves the heads from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a head suspension assembly for each head. Movement of the actuator mechanism is controlled by a voice coil motor (VCM). A printed circuit board (PCB) is mounted to the bottom of the base and contains electronic elements, which control the operation of the spindle motor, the operation of the actuator mechanism and the transfer of data to and from the discs.
In the actuator mechanism, the heads are cantilevered outward over the disc surfaces from a common pivot structure, while the coil of the VCM extends horizontally outward from the other side of the pivot structure. A magnet assembly and a pole piece structure is fixedly mounted to the base of the disc drive above the PCB in such an arrangement that the flat coil is supported in the middle of the magnetic field formed by the magnet assembly. Sophisticated control logic applies a carefully calculated amount and polarity of DC power to the ends of the coil to controllably move the coil within the magnetic field, thus moving the heads, which are fixed in relationship to the coil, across the disc surfaces.
Due to a high demand for disc drives having fast data access rates, increasingly stronger magnet assemblies have been used so that the head can be actuated faster. One problem with these magnet assemblies is that the magnetic flux that is produced cannot be completely contained within the region of the coil. As a result, stray magnetic flux impinges upon a portion of the PCB and attracts magnetic particles to the electronic elements located there. These particles can become trapped between the leads of the electrical elements resulting in electrical shorting and failure of the disc drive.
One method used to protect the electronic elements of the PCB from the effects of the stray magnetic flux is to cover or encapsulate the electronic elements that could be affected by stray magnetic flux from the magnet assembly. Here, the cover is held onto the electronic elements using a pressure sensitive adhesive. In addition to being costly to implement, one of the problems with this solution is that the operating temperature of the electronic elements increases significantly, which could lead to premature failure of the disc drive. Furthermore, reworking the electronic elements becomes more difficult. As a result, this solution is less than ideal.
Another problem found in disc drives is the generation of acoustic noise. Rapid movement of the various components of the disc drive including the rotating spindle motor, the actuator, and the discs themselves, tends to generate a wide variety of undesirable acoustic vibrations within the disc drive. These vibrations tend to be amplified by the generally highly flexible PCB of the disc drive.
It is therefore desirable to create a disc drive that reduces the effects of stray magnetic flux from the voice coil motor on electronic components on the PCB while dampening the vibration of the PCB.
The apparatus of the present invention is directed to an insert for use in a disc drive that dampens acoustic vibration and shields electronic elements from stray magnetic flux generated by a magnet assembly of a voice coil motor. The insert includes an acoustic insulator portion and a magnetic shield. The acoustic insulator portion is compressed between a base and a circuit board of the disc drive to suppress vibration of the circuit board. The magnetic shield is attached to the acoustic insulator portion below the magnet assembly and is shaped to shield a portion of the circuit board from stray magnetic flux generated by the magnet assembly.
These and various other features as well as advantages, which characterize the present invention, will be apparent upon reading of the following detailed description and review of the associated drawings.